In reading data stored on a magnetic disk, a common but unwanted occurrence is the reading of invalid data signal peaks. Unless eliminated these signal peaks impair the accuracy of the data obtained from the disk. Since the data read is typically to be utilized in other parts of a digital system, it is imperative that the data be free of error. The present invention is directed to providing error-free data while minimizing hardware costs and the amount of hardware space required to implement the invention.
In U.S. Pat. No. 3,631,263 to Graham et al., an apparatus is disclosed for separating invalid data from valid data. The apparatus is configured to permit readout data to be outputted therefrom only if four conditions are satisfied. In determining whether these conditions are met, two signal channels are employed.
Unlike the Graham et al. apparatus, the present invention generates a strobe or clock signal which is synchronous with one or more unqualified or raw data signals. A data signal is "unqualified" in that invalid and unwanted signal pulses, due to adjacent track interference, media defects, and electrical noise, may be present. In one embodiment of the invention, read information is initially converted to a single unqualified data signal and a polarity signal, which provides information relating to the polarity of the single data signal. The strobe signal is synchronous with both the unqualified data signal and the polarity signal. Another important feature of the present invention is the use of a shift register for receiving a data signal having pulses corresponding to the peaks associated with the signal read from the disk.